PRACTICAL PAPERS—BUTTER FACTORIES. 
281 
of starch into gum takes place to a considerable extent. Thus 
Vogel found that flour which contained no gum gave, when 
baked, a bread of which eighteen per cent., or nearly one-fifth 
of the whole weight consisted of gum. Thus one result of 
baking is to render the flour starch more soluble, and there¬ 
fore more easily digested. 5 ’ 
Of starch, he says: “It is a property of starch of all kinds 
to be insoluble in cold water, but to dissolve readily in boil¬ 
ing water, and to be thickened into a jelly or paste as it cools.” 
It is supposed that, by digestion, starch becomes converted 
into gum or sugar, and the latter probably becomes absorbed. 
It is also an element of respiration, and according to Liebig, 
contributes to the formation of fat in animals. This theory is, 
no doubt, well founded, and explains the fattening of animals 
when fed upon Indian corn. 
Referring to the preceding engraving, representing the coil 
heater and steamer, the only difference between it and the 
cheese vat heater is that a check-valve is substituted for the 
lower stop-cock to the tank, and the pipe furnishing the hot 
water or steam instead of extending out horizontal, is carried 
up perpendicular, and a steam separator is attached to which 
the steam pipes are connected. 
The principle of its operation is this, when the stop-cock in 
the upper pipe is open, the water in the tank circulates through 
the coil and is heated in the same manner as in the cheese 
vat heaters, but when steam is desired this stop-cock is closed, 
the return of the water to the tank is thus cut off and it re¬ 
mains in the heater until steam is generated, when the mixed 
steam and water is driven up into the separator, the water be¬ 
ing separated, runs back into the tank and the steam passes off 
through the pipes to the desired points. This will continue as 
long as the stop-cock is open. During this operation the coil 
is fed with water from the tank through the lower pipe. 
